Tanya is 12 years older than Leah. Three years ago, Tanya was five times as old as Leah was. How old is Leah?

When Leah was 3 Tanya would have been 15. Three years later Leah would be 6. There was only one time when Tanya would have been five time as old as Leah. It is just a matter of adding three more years to Leah's age.